Archives: Book Pages

This is the book page

10.2.1. C-Space Obstacles

This video introduces the notions of C-space (configuration space) obstacles, connected components of the free configuration space, and collision detection.

10.2.3. Graphs and Trees

This video introduces graph representations of free C-space, including undirected and directed graphs, weighted and unweighted graphs, and trees.

10.2.4. Graph Search

This video describes A* graph search, one of the most popular and efficient methods for finding optimal paths in a graph.

10.3. Complete Path Planners

This video introduces roadmap methods for complete path planning: if a path exists, then a roadmap method is guaranteed to find one. Such methods tend to be applied to only simple, low-dimensional problems, however. One example, given in the video, is path planning for a planar polygon translating among polygonal obstacles.

10.4. Grid Methods for Motion Planning

This video introduces grid methods for path planning, where the free C-space is represented by a regular grid that can be searched using standard graph search methods (e.g., A*). To increase efficiency, multi-resolution grids can also be employed.

10.6. Virtual Potential Fields

This video introduces the virtual potential field method for reactive motion planning, where obstacles are at a high potential and the goal is at the minimum potential. The negative of the gradient of the potential is a force that pushes the robot away from obstacles and toward the goal.

Chapter 11 Autoplay

Autoplay of the YouTube playlist for all videos in this chapter.  This description box will not be updated with information about each video as the videos advance.

11.1. Control System Overview

This video introduces different robot control objectives (motion control, force control, hybrid motion-force control, and impedance control) and typical block diagram models of controlled robots.

11.2.1. Error Response

This video introduces the error response for a controlled system and characterizes the error response in terms of its steady-state error and its transient response (overshoot and settling time).

11.2.2. Linear Error Dynamics

This video introduces linear error response, where the error dynamics are represented by a linear ordinary differential equation, which can also be represented as a set of coupled first-order differential equations, xdot = Ax. Stability of the error dynamics is achieved if the real components of the eigenvalues of A are all negative, or, equivalently,

11.2.2.2. Second-Order Error Dynamics

This video studies error dynamics modeled as a second-order linear ordinary differential equation. Stable error dynamics are characterized as overdamped, critically damped, or underdamped.

11.3. Motion Control with Velocity Inputs (Part 2 of 3)

This video introduces proportional-integral (PI) control of the position of a single-degree-of-freedom system, and feedforward plus PI feedback control, for the case where the desired position is a ramp as a function of time (constant velocity) and the control input is the velocity. The approach generalizes easily to the control of a multi-degree-of-freedom robot.

11.3. Motion Control with Velocity Inputs (Part 3 of 3)

This video addresses task-space motion control of a robot, where the control inputs are the joint velocities and the desired motion of the end-effector is expressed as its configuration X in SE(3) and the end-effector velocity is expressed as a twist. The proposed control method is a feedforward plus PI feedback controller.